go vet and lint

* Naming
    * If this is not some OpenPGP standard I follow rule that `DES` should be
      upper case as it is abreviation and `Triple` should be camel-case as it
      is normal word hence `TripleDES`
    * rename `errors2` -> `errorsPGP`
* long lines
    * https://github.com/golang/go/wiki/CodeReviewComments#line-length
    * I bit improved long lines based on my folding
    * reuse type in definition if possible i.e. `a string, b string, c string` -> `a,b,c string`
    * `if long_statetent(); err!=nil {` -> `long_statement;↵ if err!=nil {`
    * spaces around operators (e.g. `a + b` -> `a+b`)
* removing empty lines on start and end of scope
* comments
    * on all exported functions
    * start with function name
* import:
    * order in alphabet
    * separate native, golang.org/x/ and our libs

crypto/attachment_test.go

@@ -1,14 +1,16 @@
 package crypto
 
 import (
-	"github.com/stretchr/testify/assert"
 	"encoding/base64"
 	"io/ioutil"
 	"strings"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
-// const testAttachmentEncrypted = `0ksB0fHC6Duezx/0TqpK/82HSl8+qCY0c2BCuyrSFoj6Dubd93T3//32jVYa624NYvfvxX+UxFKYKJxG09gFsU1IVc87cWvUgmUmgjU=`
+// const testAttachmentEncrypted =
+// `0ksB0fHC6Duezx/0TqpK/82HSl8+qCY0c2BCuyrSFoj6Dubd93T3//32jVYa624NYvfvxX+UxFKYKJxG09gFsU1IVc87cWvUgmUmgjU=`
 
 func TestAttachmentGetKey(t *testing.T) {
 	testKeyPackets, err := ioutil.ReadFile("testdata/attachment_keypacket")
@@ -22,7 +24,11 @@ func TestAttachmentGetKey(t *testing.T) {
 		t.Fatal("Expected no error while decoding base64 KeyPacket, got:", err)
 	}
 
-	split, err := SeparateKeyAndData(testPrivateKeyRing, strings.NewReader(string(testKeyPacketsDecoded)), len(testKeyPacketsDecoded), -1)
+	split, err := SeparateKeyAndData(
+		testPrivateKeyRing,
+		strings.NewReader(string(testKeyPacketsDecoded)),
+		len(testKeyPacketsDecoded),
+		-1)
 	if err != nil {
 		t.Fatal("Expected no error while decrypting attachment key, got:", err)
 	}